The present invention relates to a laminated glass and an automobile employing it.
In recent years, it has become common to use an infrared shielding window glass as a window glass for an automobile for the purpose of suppressing a temperature increase in the automobile and reducing the cooling load. As a conventional infrared shielding window glass, a thin film-attached glass plate is used which is prepared by laminating a thin film of various metal or metal oxide on the surface of a glass plate, whereby by the function of such a film, a solar radiation energy entering into the car can be substantially reduced.
However, the above thin film has electrical conductivity, and it tends to reduce radiowave transmittance of a window glass and thus is likely to bring about a trouble in the function of an antenna for a radio, TV or GPS (Global Positioning System) provided on the window glass. Such an antenna is prepared by a circuit pattern (such as a sintered body of a conductive ceramic paste) printed on the inside of e.g. a rear window glass. Therefore, in order for the printed pattern to maintain the function as an antenna, the window glass is required to have a high radiowave transmittance.
To solve such a problem, JP-A-8-259279 proposes a laminated glass for shielding infrared rays while securing the radiowave transmittance. This laminated glass has an interliner having functional fine particles having a particle size of at most 0.2 xcexcm incorporated and dispersed therein and is said to be able to shield infrared rays and to reduce radiowave reception difficulty.
For example, JP-A-8-259279 discloses, as Example 6, a laminated glass prepared by sandwiching between glass sheets an interliner prepared by adding 7 g of DIDP (diisodecyl phthalate) having 20 wt % of ITO ultrafine particles (particle size: at most 0.1 xcexcm) incorporated and dispersed therein and 95 g of usual DIDP, to 323 g of a PVB resin. Namely, a laminated glass is disclosed wherein a clear glass sheet having a thickness of 2 mm and a green glass sheet having a thickness of 2 mm are bonded by an interliner having ITO ultrafine particles incorporated and dispersed therein (corresponding to an interliner having about 0.3 (≈0.2xc3x977÷(7+95+323)xc3x97100) part by mass of ITO ultrafine particles incorporated to 100 parts by mass as the total mass of the interliner). This laminated glass has a sufficient solar radiation transmittance and at the same time has realized a low haze, such that its solar radiation transmittance Ts is 42.0%, and the haze H is at a level of 0.2%.
However, in this Example 6, the content of ITO ultrafine particles is small, whereby transmittance of near infrared rays can not be adequately suppressed, thus leading to an increase of the surface temperature of a car interior seat or a steering wheel and an increase of the interior temperature. Further, if the proportion of ITO ultrafine particles is increased to increase the shielding performance against lights with wavelengths within the near infrared ray region, troubles in various systems employing infrared data communication, are likely to occur.
For example, in recent years, VICS (Vehicle Information and Communication System) employing an optical beacon has been widely used in Japan. This is a system to prevent traffic jam, etc., by communicating traffic information collected by an information center to each automobile and at the same time communicating information on the automobile side to the information center. Specifically, infrared data communication is carried out in both directions between a device installed at the road side (hereinafter referred to as a road side antenna) and a device installed in an automobile (hereinafter referred to as an in-vehicle device).
Further, a keyless entry is a system to carry out opening and closing a door lock by sending an infrared signal to a light receptor in an automobile by using a light emitter which the owner of the automobile has. Thus, in order to let such a system operate normally, the window glass is required to have an infrared transmittance. Particularly for such a system, an infrared light having a wavelength of about 850 nm is employed.
Accordingly, a window glass for an automobile is required to have a nature to let an infrared light having a wavelength of about 850 nm permeate sufficiently. However, addition of ITO powder for heat shielding serves not only to shield an infrared light having a wavelength in the vicinity of from 1,000 nm to 2,000 nm but also to shield an infrared light having a wavelength of about 850 nm, whereby there has been a problem that the infrared data communication tends to be difficult.
It is an object of the present invention to solve such a problem of the prior art and to provide a laminated glass which shields an infrared light having a wavelength of at least 1,000 nm which causes an increase of the interior temperature, and which permits permeation of an infrared light having a wavelength of about 850 nm useful for infrared data communication, and to provide an automobile employing such a laminated glass.
To accomplish this object, the present invention provides a laminated glass comprising a plurality of glass sheets laminated one on another with an interliner provided between the respective adjacent glass sheets, characterized in that said laminated glass has at least a first region and a second region, as viewed from the front, and at the second region, said laminated glass has an infrared transmittance higher than the infrared transmittance at the first region.
In a preferred embodiment, the visible light transmittance of said laminated glass at the second region is lower than the visible light transmittance of said laminated glass at the first region.
Still further, the present invention provides an automobile provided with said laminated glass and an in-vehicle device for infrared data communication with an external device via the second region.